Article,
Modeling auditory processing of amplitude modulation. I. Detection and masking with narrow-band carriers
Acoustical Society of America, (1997)
Abstract
This paper presents a quantitative model for describing data from
modulation-detection and modulation-masking experiments, which extends
the model of the ‘‘effective’’ signal processing of the auditory
system described in Dau et al. J. Acoust. Soc. Am. 99, 3615–3622
(1996). The new element in the present model is a modulation filterbank,
which exhibits two domains with different scaling. In the range 0–10
Hz, the modulation filters have a constant bandwidth of 5 Hz. Between
10 Hz and 1000 Hz a logarithmic scaling with a constant Q value of
2 was assumed. To preclude spectral effects in temporal processing,
measurements and corresponding simulations were performed with stochastic
narrow-band noise carriers at a high center frequency (5 kHz). For
conditions in which the modulation rate ( fmod) was smaller than
half the bandwidth of the carrier (Df ), the model accounts for the
low-pass characteristic in the threshold functions e.g., Viemeister,
J. Acoust. Soc. Am. 66, 1364–1380 (1979). In conditions with fmod.Df
/2, the model can account
for the high-pass characteristic in the threshold function. In a further
experiment, a classical masking paradigm for investigating frequency
selectivity was adopted and translated to the modulation-frequency
domain. Masked thresholds for sinusoidal test modulation in the presence
of a competing modulation masker were measured and simulated as a
function of the test modulation rate. In all cases, the model describes
the experimental data to within a few dB. It is proposed that the
typical low-pass characteristic of the temporal modulation transfer
function observed with wide-band noise carriers is not due to ‘‘sluggishness’’
in the auditory system, but can instead be understood in terms of
the interaction between modulation filters and the inherent fluctuations
in the carrier.
